Steering bearings are used in different designs. Often, the steering spindle is mounted, at least in the upper part of the steering column, with help of two angular contact ball bearings that are placed under pre-stress against each other. The angular contact ball bearings comprise bearing rings made out of sheet metal by cold forming.
As a rule, the outer ring is pressed directly into the steering tube. In case of high tolerances of the steering tube, this can also be seated with help of a tolerance ring in the tube. In both cases, as a rule, the axial positions of the outer rings are determined through an axial stop. As a rule, the axial stops are formed in each case by the end of the steering column tube.
The points at which the inner ring of the respective steering bearing is supported on the surface of the steering spindle are defined through the position of the steering spindle relative to the steering column tube and the permissible deviations of this position. However, the points are also influenced by the shape and dimension tolerances of the steering spindle, of the steering column tube, and of the steering bearings themselves, and, in the case of angular contact ball bearings, also by their elastic inward yielding during assembly.
The inner ring of a first steering bearing of the steering column is axially fixed on the steering spindle. The inner ring of a second steering bearing situated axially opposite the first steering bearing is biased against the balls of the second steering bearing through the spring force of one or more spring elements acting on a clamping ring. In this way, the inner ring is centered radially relative to the central axis of the steering spindle with help of the clamping ring and fixed on the steering spindle. The clamping ring keys itself with an edge radially between the inner ring and the surface of the steering spindle. The pre-stress of the spring element is maintained with help of a securing element which usually is an indented ring. The indented ring claws itself into the surface of the steering spindle.
In order to assure a cost-effective manufacturing, steering spindles comprise relatively large shape and dimension tolerances in the cylindrical outer contour. Dimension deviations of nominal values of up to 2/10 mm or more can easily occur on the seat of the steering spindle through interaction with the inner ring. The clamping ring therefore comprises tolerance-compensating functions of a tolerance ring. Due to the tolerances, the diameter of the inner ring at the bearing seat on the steering spindle is therefore so large that, even in the case of unfavorable tolerance conditions, the inner ring and the clamping ring do not come directly into contact with each other at the shaft seat of the inner ring. At the shaft seat, the inner ring is supported through the clamping ring on the steering spindle.
One example of the above-described arrangement is shown in EP 0941 414 B1. The steering column in this arrangement comprises an angular contact ball bearing comprising a plastic clamping ring, a spring element configured as a wavy spring and a securing element configured as an indented ring.
Such arrangements have often stood the test. However, the multiplicity of parts of which the steering column is made, is a drawback with regard to storage, logistics and assembly. Therefore, efforts have been made in the past to reduce the multiplicity of parts to a minimum.
DE 100 27 513 A1 shows such an arrangement with an angular contact ball bearing whose inner ring is made in one piece with the securing element. The securing element is made after the manner of an indented ring with a plurality of peripherally spaced apart tabs all of which mostly have a sharp edge. In the non-assembled state of the angular contact ball bearing, the edges define a central recess that is described by a circular line and whose diameter is somewhat smaller, all tolerances taken into consideration, than the smallest outer diameter of the steering spindle so as to overlap this. Due to the overlap during pressing of the inner ring onto the steering spindle, the tabs claw themselves with the edges into the surface of the steering spindle and hold the inner ring in position. During this process, the tabs yield elastically inwards. Under certain circumstances, this, in itself good solution, can have a detrimental effect on the rigidity of the bearing arrangement. When the steering spindle is loaded by the steering wheel, the inner ring can either yield too strongly inwards thus causing an excessive inclination of the steering spindle, or the vibration behavior of the steering spindle can be disadvantageously influenced.
In the generic arrangement described in DE 10 2009 051 107 B3 therefore, a press fit of the inner ring on the steering spindle is provided in addition to the above-described securing ring. The inner ring of the arrangement described in DE 10 2009 051 107 B3 comprises, on one end, the securing element after the manner of an indented ring, and on the other end, a bearing seat. Due to the double support, the arrangement is more rigid. A raceway section for the rolling elements is configured axially between the securing element and the bearing seat. During mounting of the angular contact ball bearing, the inner ring is pressed with the bearing seat onto the steering spindle so that the tabs of the securing element claw themselves with the edges into the surface of the steering spindle.